Haylage is produced from freshly cut grass, usually an earlier cut than the first hay cut, then wrapped in several layers of plastic to retain a high moisture content. It then ferments via lactic acidification which  'preserves' it.

This lactic acidification/fermentation occurs courtesy of Lactic-acid (LA) bacteria, and if you've read our main Gut System page you'll already have a fair idea as to why this isn't great news for the horse's fragile gut microbiome ecology. LA bacteria are consumed by the horse when the horse eats haylage, but - they're not a recognised colony member of the equine gut biome, and worse, they're a pro-inflammatory bacteria, making them a very unwelcome imposter taking up residence in the hindgut. See our Gut System/Hindgut Acidosis page for the full story.

By their very nature, LA bacteria burp out lactic-acid gas as their waste, so overall the whole lactic-acid subject is about uninvited acidic gas in the intestines where it doesn't belong. Why? It creates an acidic intestinal pH value of below 3, sometimes dropping as low as 1.3, whereas the intestinal environment should always remain at a neutral pH of around 7. This means we're talking red-hot, raw, acidic burn, which is very uncomfortable in itself, let alone the pressure from the inflammatory lactic-acid gas now bloating out the intestines.

Let's now factor in the grass species that most haylage is made from, and it's the equine grass nemesis - rye. It's ideal from a haylage-producing business perspective because rye grows fast - it was genetically designed this way for farmers to get big dairy and meat yields from it, unlike meadow grass. Rye is also resistant to the buffet of chemical sprays - fungicides, herbicides, pesticides, fertilisers et al, so producers can easily get 3-4 crops a year. It also contains endophytes which are a known equine toxin, known to trigger both laminitis and foal abortion. Sorry ...

But ... perhaps worst of all for the horse, rye grass can contain up to a whopping 36% sugars 😮. Yes you read that right. So just for this reason alone, as horse carers we should definitely be rethinking feeding haylage.

Let's get back to those pesky LA bacteria. Being a sugar-loving pro-inflammatory bacteria, the LA bacteria start feeding from the sugar (and protein) in the diet but unlike the equine-friendly hindgut fibre-fermenters, LA bacteria don't produce any beneficial nutrients, only LA gas as a waste product. This is bad news - due to the now acidic pH value in the intestines creating hindgut acidosis/dysbiosis/SIBO, the intestinal mucous membrane wall becomes inflamed and breaks open like a zipper being pulled apart. Cue Leaky Gut syndrome, which as we know leads to major toxicity-related health issues throughout the body, and one of the many causes of faecal water syndrome in horses.

These days? Hindgut acidosis is prevalent everywhere - it's certainly a factor in most of our client consults. It's vital that we do everything we can to prevent LA bacteria getting in the hindgut/cecum as it lowers the pH to aggressively sour levels, creating a toxic state of dysbiosis in the gut biome, which as we well know leads to a downward health spiral. For the record, my connie, Murphy, can't touch haylage - he loves it (what horse wouldn't?!) but his gut is completely intolerant of it. He literally goes into almost immediate projectile faecal-water stable wall-art mode.

The hindgut is also where two of the vital equine-appropriate 'activated' B-vitamins are produced, B6 (P5P) and B12. Lactic-acid halts this production, which then triggers significant effects on the entire metabolic process and, among other things, promotes the occurrence of a detoxification disorder known as Cryptopyrroluria (KPU). This is still relatively new science (2020), with KPU a relatively new label to reach the mainstream, so much is still to be learned about it. However, what is known is that it significantly affects the gut:liver:kidneys pathway and lymphatic function, in other words the horse's natural - and very sophisticated - in-built detoxification system.

There's also a myth relating to haylage supposedly being a high energy source. Wrong. Its alleged high protein value is due to bacterial protein from the LA bacteria, not a beneficial equine-appropriate protein for the digestive enzymes to break down into amino acids to be utilised. Equally, due to the disruption in the hindgut's fibre-fermenting biome, the vital volatile-acid energy source created from the digesting plant cellulose-fibre (butyrate, acetate, proprionate) is disrupted, therefore unable to effectively provide the horse with the energy it needs.

Lactic-acid presence creates an immensely negative burden on the horse's body. If present it can be coverted into glucose by Veillonellaceae bacteria, but the body isn't able to adequately convert the ever-increasing large amounts, so the burden on the detoxification organs means they've got to store it somewhere till the excretion queue goes down. Cue the connective tissue - we're talking tendons/ligaments/muscles/sheath swelling and so on.

This results in what looks like weight gain or inflammation, so out comes the vet who will take bloods (rightly), but assume it's an infection (wrongly) and prescribes antibiotics and bute. A few days later the blood results come back saying 'liver disease'. Wrong. Liver overwork due to toxic overload. (We have a perfect testimonial to this effect on our LiverCARE product page).

It's all about digging down for the root cause and connecting the dots! It's not about inflammation or an increase in muscle mass or fat - it's about the storage of lymph in the tissue, which is trying to dilute the acid in the soft tissue. This hyperacidity can't be seen in the blood count because the kidneys - who regulate just about everything in the body - are working overtime to keep the blood pH constant (more on the awesome job(s) the kidneys do in our Kidneys page). Next to the intestines, the kidneys are the next most damaged organ from feeding haylage.

This storage of acid in the connective tissue also has a knock-on effect on how the horse performs - yet another haylage effect, this time on the musculoskeletal system. If your horse is hard to ride, if they're a bit stiff, if it's hard to get them going, if they have tendonitis or swollen legs, and if this is all accompanied by a general overall reluctance, it could all be due to the LA making the muscles too acidic.

Finally, any forage wrapped in plastic will ferment and change the pH, so that means drylage as well - there's always the risk of bacteria, yeast and mould surviving. Dry haylage has a pH of around 6 which means bacteria, yeast and mould can survive. There's also the grim risk of fermented dead animals in the haylage, i.e. field mice, which trigger Chlostridium botulinum bacteria. This will rapidly spread throughout the whole bale, unlike in a hay bale where the dead mouse doesn't ferment because there's no humid fermenting environment, so at least in hay the decay will remain static.

(GRIM STATS - Botulism poisoning has been known to cause fatal poisoning in horses from dead mice found in haylage - 98% of horses will not survive chlostridium poisoning. Stats from Germany show up to 100 horses/year die from it, and what is known is that these horses were all fed on haylage. This is serious stuff, and yet the horse-community isn't even talking about it!)

To summarise

• Haylage is predominantly produced from rye grass, which is grown on a mass-produced scale, heavily chemically sprayed, contains a known equine-toxin, and sugars exceeding 35%.

• Haylage contains LA bacteria, which creates lactic acid gas in the intestines.

• The hindgut environment is basically a big fermentation vat, and it's hot! Which makes it a perfect breeding ground for LA bacteria; dysbiosis can appear in just 3-weeks - https://academic.oup.com/jas/article/87/7/2291/4731169?login=true

• Zinc is needed to help neutralise the acid, so another vital reason to feed a mineral balancer.

• Haylage also puts extra work on the liver, as the liver needs activated vit. B6 - P5P - (produced in the hindgut) to biotransform (metabolise) the lactic acid so it can be sent to the kidneys for excretion via the urine. However, the LA bacteria evolve quicker than they can be excreted, which puts enormous extra strain on the liver, while having to cope with a P5P deficiency due to the hindgut dysbiosis preventing its production.

• There's less equine-appropriate 'energy' created in haylage.

• There's also a 'wrong type of grass' issue. If grass is cut late for haylage, i.e. when the grass has seeded and become coarse and stemmy (the best grass for the best hay/fibre), this is difficult to ferment into haylage as the LA bacteria won’t find enough of its preferred nutrient energy source - starch/sugars - to produce enough lactic acid to get a pH lower than 5 to ferment the grass into haylage.

• It's said that "one winter on haylage may lead to a complete wipeout of the hindgut biome". (Quote - Dr Christina Fritz)

Of course there'll be many people shouting out that their horses are fine on haylage. I get this - a couple of winters on haylage and all may seem fine for typically the less metabolic, native-type horse or pony. However, it's all about accumulation - the systemic acidic haylage-effect takes time to accrue before we see symptoms - around 2-3 years, so don’t be misled into thinking a horse is fine on haylage.

And ... any haylage producer will quite rightly endeavour to assure you that haylage is fine, so why wouldn't we be assured? After all, no-one would knowingly want to feed their horse something that may negatively affect them. As it happens, one of our clients, while investigating their own horse's hindgut issues, contacted their supplier and received the following reply:

"Haylage itself doesn't produce lactic acid in the horse. During the conservation process in an anaerobic environment, lactic acid bacteria are at work within the wilted grass. The higher the moisture content of the forage, the more lactic acid is produced by these bacteria within the grass. Our Haylage has a very high dry matter (very little moisture, compared to a Haylage made much wetter or a silage) and so therefore minimal lactic acid levels are produced. Certainly nothing at levels anybody including independent nutritionists and vets have reason to be worried over. Some people may be referring to behavioral changes bought on by example hind gut acidosis where significant amounts of lactic acid is produced in the hind gut as a result of too much starch.

My thoughts:

• Haylage itself doesn't produce lactic acid in the horse. 
  
  Hmmm, in theory, it doesn’t produce LA, but in practice it kind of does. Haylage acts as the carrier for the LA bacteria which then get into the hindgut. By their very nature these bacteria thrive on sugar/starches so as they’re travelling through the small intestine where sugars/starches are digested enzymatically, they’ll have a good old feed as they’re passing through and onwards to the large intestine (hindgut), so straight away they’ve been fuelled to multiply. And once in the nice hot fermentation vat that is the colon, they’ll multiply even more, and so the ripple effect begins, with them outnumbering and killing off the beneficial fibre fermenters and burping out their acid gas waste as they go.
  
  
• During the conservation process in an anaerobic environment, lactic acid bacteria are at work within the wilted grass. The higher the moisture content of the forage, the more lactic acid is produced by these bacteria within the grass. Agree. Our Haylage has a very high dry matter (very little moisture, compared to a Haylage made much wetter or a silage) and so therefore minimal lactic acid levels are produced.
  
  Still LA bacteria though, which by the very nature of bacteria, they multiply. 
  
  To quote from Applications of Biotechnology to Fermented Foods: Report of an Ad Hoc Panel of the Board on Science and Technology for International Development / 5. Lactic Acid Fermentations: "As would be expected, the rate of completion of the fermentation depends on the temperature and salt concentration. At 7.5°C fermentation is very slow: under these circumstances, Lactobacilli grows slowly, attaining an acidity of 0.4 percent in about 10 days and an acidity of 0.8 to 0.9 percent in a month. Lactobacilli cannot grow well at this temperature, and the fermentation may not be completed for 6 months. At 18°C a total acidity (as lactic acid) of 1.7 to 2.3 percent will be reached, with an acetic to lactic acid ratio of 1:4, in about 20 days. At 32°C a similar activity will be reached in 8 to 10 days, with most of the acid being lactic acid produced by the homofermentative bacteria Lb. plantarum and P. cerevisiae.” Note - this last temperature being much nearer a horse’s rectal temperature reading.
  
  
• Certainly nothing at levels anybody including independent nutritionists and vets have reason to be worried over. Some people may be referring to behavioral changes bought on by example hind gut acidosis where significant amounts of lactic acid is produced in the hind gut as a result of too much starch. 
  
  Disagree. Acid-osis! Caused by the acidic gas released by lactic acid bacteria lowering the pH value significantly. Not starch-osis. The only time you may see too much starch in the hindgut is from  haylage produced from rye, which no horse should be eating anyway.

Overall, haylage may lead to reduced performance of the horse and potential long-term damage to health, where the consequences are often only noticeable years later and therefore rarely put into direct context - https://www.nature.com/articles/ismej200867